When cancer survivors exercise for several weeks after they finish chemotherapy, their immune systems remodel themselves to become more effective, and they can potentially fend off future cancers. This preliminary study may help to explain why exercise significantly reduces the chance of secondary cancer in survivors or reduces the chances of cancer altogether in people who have never had the disease.

Laura Bilek, PT, PhD, of the University of Nebraska Medical Center and the study leader, explained that previous research had found positive associations between exercise and cancer. Exercise can reduce the risk of getting initial incidences of several different types of cancer, can often improve prognosis in cancer patients, and can reduce the risk of recurrence and secondary cancers in survivors of some types of cancer. The mechanism behind these phenomena was unknown.

This study investigated how exercise affects the immune system of cancer patients. T cells in the blood of 16 cancer survivors, all but one of whom had recently completed chemotherapy, were analyzed before and after a 12-week exercise program. After chemotherapy, the majority of T cells become senescent, which is a form that is less effective at combating disease than the naïve form, which is ready to fight cancer and infections. After the individualized, 12-week exercise program, the ratio of senescent to naïve T cells changed favorably in a majority of the participants. Most study subjects regained greater numbers of the naïve variety to T cells.

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“What we’re suggesting is that with exercise, you might be getting rid of T cells that aren’t helpful and making room for T cells that might be helpful,” Bilek says. “There’s a litany of positive benefits from exercise. If exercise indeed strengthens the immune system and potentially improves cancer surveillance, it’s one more thing we should educate patients about as a reason they should schedule regular activity throughout their day and make it a priority in their lives.”

This research was presented at The Integrative Biology of Exercise IV meeting held October 10-13, 2012, in Westminster, Colorado.